When alternating current (AC) power is supplied to an electric device such as a server or a storage device, an input current with an amount that is several times higher than an operating current may flow. The input current is called an inrush current (or a striking current).
The inrush current may occur due to charging a capacitor included in a power supply circuit arranged in the electric device. In this case, the occurrence of the inrush current is largely affected by the charging. In order to generate a direct-current voltage with a small pulsating component, an input smoothing capacitor with a large capacity is arranged in the power supply circuit on the input side of the power supply circuit. When the input smoothing capacitor is in an initial state, the amount of charges in the input smoothing capacitor is close to 0. Thus, when power is supplied, a large charging current instantaneously flows and becomes the inrush current.
When the inrush current occurs, a current that is larger than a rated current flows in a power supply line and may damage a circuit element or a connector. It is, therefore, important to suppress the inrush current in order to stably operate a system. Thus, the following technique has been proposed: a technique for inhibiting the occurrence of an inrush current when power is supplied or when a system is restored after an instantaneous power failure.
Japanese Laid-open Patent Publications Nos. 10-155272 and 11-196529 are examples of related art.
In recent years, with reductions in the sizes of electronic devices such as servers and storage devices and increases in the densities of the electronic devices, the number of various electronic devices capable of being placed in the same rack has increased. There is a problem that the larger the number of electronic devices placed in the same rack, the larger an inrush current that occurs in a whole system.
Since an inrush current occurs in each of power supply circuits included in the electronic devices, a method for controlling an electronic device and a level to which an inrush current is suppressed vary depending on a power supply circuit included in the electronic device. Thus, an inrush current suppressing circuit is arranged for each of the power supply circuits in many cases. There is, however, a problem that, for a configuration in which an inrush current suppressing circuit is arranged for each of power supply circuits included in electronic devices, as the number of electronic devices is increased, the cost for suppressing an inrush current increases.